Induction Heat-Treating Apparatus and Process

ABSTRACT

An apparatus for induction heat treating and quenching a metallic part with rolls to convey, guide and restrain the part during processing. The apparatus includes a heating coil assembly with two sections of coils wound in opposite directions. The apparatus may include a quenching station with individual quenching sections having different pressures and flows of a liquid. A process for induction heat treating and quenching a metallic part in a series of rolls includes induction heating the part in a counter-wound coil assembly; quenching the part with a liquid while under restraint, and induction heating the part again after quenching. Controlling varying speed and the proximity of the metallic part to the coil assembly is ideal.

CROSS REFERENCE TO RELATED APPLICATION

This application asserts priority from U.S. provisional application61/870,738, filed on Aug. 27, 2013, U.S. non-provisional applicationSer. No. 14/468,996, filed on Aug. 26, 2014, and PCT applicationPCT/IB2014/001625, all of which are incorporated herein by reference.

FIELD OF THE DISCLOSURE

This disclosure relates to an induction heat-treating apparatus and arelated process. More specifically, the disclosure relates to heattreating a part, such as a side rail, with controlled speed of the partand the part proximity to heating coil assembly with coils that arepreferably counter-wound.

BACKGROUND

Apparatus have been devised for heat treating structural members, suchas vehicle side rails. Parts, such as side rails, are presently heattreated in relatively large furnaces with a high volume capacity. Theinvestment and scale of such furnaces are both large.

U.S. Pat. No. 4,394,194 discloses a method and apparatus for inductionheat treating and restraint quenching structural members of carbonsteel, to a uniform martensitic structure, such that distortion of themember due to rapid quenching is controlled to a minimum. Morespecifically, the member is generally heated by induction in two stagesgenerally to an austenitizing temperature in the range of 1450 degreesto 1750 degrees F. Then the member is liquid quenched under restraint tobelow 1000 degrees F. to minimize distortion and finally tempered underrestraint at a temperature in the range of 750 degrees to 1250 degreesF. Such structural members attain minimum physical properties after heattreating in the range of 110,000 psi yield strength and 125,000 psitensile strength.

Prior art FIG. 1 is sourced from the “194 patent and as disclosedtherein, FIG. 1 shows a heat treat line for the treatment of carbonsteel channel-shaped structural members 20. An entry table 22 stacks andpresents the structural members 20 in a sequential and singular fashionto the conveyor rolls 24 found at the lower edge of entry table 22. Asthe structural members 20 are fed from the entry table 22 onto theconveyor rolls 24, the conveyor rolls 24 will convey the structuralmembers 20 to the point of entry into the vertical side guide andrestraint rolls 26 and 54.

The combination of the vertical side guide and restraint rolls 26 and 54and the last succeeding or first leaving conveyor rolls 24 are used oneach end of the heat treat line so as to formulate a combination systemof rolls. The configuration of the vertical side guide and restraintrolls 26 is particularly suited to the containment of the structuralmember 20 in both horizontal and vertical alignment for entry andleaving from the heat treat line as seen in FIG. 1.

It can also be noted from FIG. 1 that the direction of travel isindicated by the directional arrows seen from the entry table onto theline and in line from left to right as shown in FIG. 1 to the exit pointonto the cooling table 23.

At such time as the structural member 20 enters the vertical side guideand restraint rolls 26, the structural member 20 then commences itsentry into the first of the heating stations which contains a preheatingcoil 28. As the structural member 20 exits the preheat coil 28, itencounters a first set of pinch rolls 30. It is this set of pinch rolls30 that drives the structural member 20 to the next set of heatinduction coils 32 while maintaining vertical restraint on structuralmember 20. Between the two heat induction coils 32 there is a supportingroll assembly 34 which supports the structural member 20 in correctvertical alignment for entry into the second set of heat induction coils32.

As the structural member 20 exits the second set of heat induction coils32, it enters a second set of pinch-restraint rolls 36. Thepinch-restraint rolls 36 drive the structural member 20 into the quenchzone 40. In this quench zone 40, the structural member 20 is surroundedon all sides by the multiplicity of liquid supplies 44 which through aseries of apertures will supply an ample amount of liquid to quicklyreduce the temperature of the structural member. Additionally at theexit end of the quench zone 40, sets of guide rolls 48 assures that themember 20 progresses evenly and steadily to the pinch rolls 30 whichnext drive the structural member 20 to the next set of pinch rolls 30 toprepare the material for the next stage of processing.

Next follows the tempering section with an induction coil 50 in whichthe temperature of the structural member 20 is again raised. Immediatelyfollowing the tempering section with induction coil 50 is another set ofdrive pinch rolls 36. Following the drive pinch rolls 36 are furthersets of vertical restraint rolls 54 and 26 restraining the flangemembers of the structural member 20 so as to assure the trueconfiguration of the structural member 20 through the final stage ofprocessing. The final set of rolls utilized in the processing stage arethe exact mirror image of the very first set of rolls used in theprocessing stage. Finally, the structural member is conveyed to the endsof the conveyor rolls 24 and then moved laterally onto the coolingtables 23.

Each of the induction heating coils 28, 32 and 50 are fitted with analternating current through a generation system which will producevarying frequencies. These heat stations 56 are individualized so as tofeed each one of the heating induction coils 28, 32 and 50 with therequired power of alternating current to produce the most energyefficient means of heating the structural member 20 to the desiredtemperature ranges.

That method and apparatus for induction heat treating are specificallydisclosed for use with a truck side rail as the heat-treated part.

Adaptions are needed from the current methods and apparatus to make themwork better, including more practical frequencies and temperatures witha properly scaled project. A higher efficiency apparatus and method aredesirable with better control and less distortion of the heat-treatedpart.

SUMMARY

The present disclosure provides induction heat-treating apparatus andprocess for heat-treating parts. This system is well suited for siderails of a vehicle as the heat-treated part.

The induction heat-treating apparatus and processes include improvementsover the apparatus and method disclosed in U.S. Pat. No. 4,394,194. Nopreheating is required with the presently disclosed inductionheat-treating apparatus and process. The relationship between speed inwhich a part passes through the process and the heating coil sizeassists with avoiding a preheating requirement. Previously preheating atdifferent temperatures required two frequencies and power sources.

The present counter-wound design with a space separating the heatingcoils allows the temperature to be leveled. The coils can use the samefrequency and power source with the present design.

A relatively slow speed of less than 100 inches per minute avoids alarge hot area on a treated part and the resulting problematicdistortion of such part. Varying the exit speed of the part from theprocess and the entrance speed of the part into the process can be afactor for this apparatus and process. While the speed of advance of apart through the heat treat system is known to influence operatingconditions, the change in speed via acceleration or deceleration atentry, through specific sections and at exit can now be controlled viacomputer for enhanced performance and characteristics of the part.

Also, a defined distance between the part and the heating coil assembly(part proximity) affects the heat-treating performance. The partproximity can be set to maximize the heat treating benefits for thepart. While sometimes set at a predetermined distance, the partproximity be controlled for enhanced performance and characteristics ofthe part.

Next, two coil sections of the heating coil assembly preferably wind inopposite directions. The induction on some heating coils is done fromone distal end of the coil section to the other extreme, and a secondcoil section is wound the other way around. The opposing winding helpsavoid the part being pushed by the “electricity force” or in otherwords, the electromagnetic forces generated by the induction coils, andtherefore being distorted by such pushing force or electromagneticforce.

The counter-winding also provides magnetic neutralization, which resistsmaterial from ionization. This results in less rusting of the materialand better durability of the part.

The coil sections are provided in a configuration in which the coilsection encircles the part being heat treated, and in which the coilsection has a geometry that provides a varied spacing of the coilsection from the part along the part surface so that the heating of thepart is uniform and deformation is reduced or avoided, regardless ofpart geometry.

Also, the apparatus preferably has individual quenching sections (withdifferent pressures and flows) to maximize physical properties of thepart. Quenching with liquid is done longitudinally, but alsoperpendicularly to minimize distortion of the part. Partitioning in eachquench plane (up, down, right, and left) is controlled in the quenchingprocess, which can avoid part distortion, such as camber, twisting andbowing. This solves some of the distortion concerns with parts producedin continuous production.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features of this disclosure and the mannerof obtaining them will become more apparent, and the disclosure itselfwill be best understood by reference to the following descriptions ofsystems and processes taken in conjunction with the accompanyingfigures, which are given as non-limiting examples only, in which:

FIG. 1 shows a prior art schematic of a heat-treating production linefrom U.S. Pat. No. 4,394,194;

FIG. 2 shows a view of a portion of an induction heat-treating apparatushaving a heating coil assembly with sections wound in oppositedirections;

FIG. 3 shows a schematic view of the part passing through a heatingstation illustrating two sections of coil in which one section of coilis wound in the opposite direction from the other section of coil;

FIG. 4 shows the configuration of a portion of a coil surrounding thepart within the heating station; and

FIG. 5 shows an alternative configuration of a portion of a coilsurrounding the part within a heating station; and

FIG. 6 shows a view of a quenching section;

The exemplifications set out herein illustrate embodiments of thedisclosure that are not to be construed as limiting the scope of thedisclosure in any manner. Additional features of the present disclosurewill become apparent to those skilled in the art upon consideration ofthe following detailed description of illustrative embodimentsexemplifying the best mode of carrying out the disclosure as presentlyperceived.

DETAILED DESCRIPTION

While the present disclosure may be susceptible to embodiments indifferent forms, the figures show, and herein described in detail,embodiments with the understanding that the present descriptions are tobe considered exemplifications of the principles of the disclosure andare not intended to be exhaustive or to limit the disclosure to thedetails of construction and the arrangements of components set forth inthe following description or shown in the figures.

The disclosed process and apparatus are well suited for a part 58corresponding to the side rails of a vehicle, and particularlyC-channels having a C-shaped cross-section. Both can heat-treat the part58, but also minimize distortion of the part 58.

Referring to FIG. 2, an apparatus 60 for induction heat treating andquenching a metallic part 58 may have rolls to convey, guide andrestrain the part 58 along a treatment line. An entry table can load thepart 58 onto the treatment line with initial conveyor rolls andsubsequent guide rolls and pinch and restraint rolls as needed. Therolls may be computer controlled.

The line includes a heating station 62, a quenching station 64 and asecond heating station 66 before or preferably after the quenchingstation 64, wherein the second heating station 66 after the quenchingstation 64 tempers the part 58. However, the second heating station 66need not be located after the quenching station 64. With an improvedheating coil assembly 68 at the initial heating station 62, preheatingmay no longer be required.

Each heating station may include a heating coil assembly 68 with twosections of coils 70 and 71 wound in opposite directions as shown inFIG. 3 to define multiple turns 72 for each of the coil sections 70, 71.Each turn 72 essentially follows, and extends one time about, theperiphery of the part 58, with each coil section 70, 71 extendingmultiple times about the part 58. Although four turns 72 are illustratedin FIG. 3, the actual number of turns 72 will be determined by therequirements of the specific application. The counter-wound coilassembly 68 may have a section of coil 70 and 71 with initiation fromone side, and another coil with initiation on the other side of thecoil. The induction on one section of coil 70 or 71 is preferably donefrom one distal end of the coil to the other extreme, and a secondsection of coil is wound the other way around with induction in anopposite direction wherein the coil assembly 68 provides substantialmagnetic neutralization and minimal pushing force.

The apparatus 60 includes a space 74 between and separating the heatingcoils to allow the temperature of the part 58 to be leveled. The coilsections 70 and 71 can use the same frequency and power source for theheating coil assembly 68, wherein the power (kW) and frequency (kHz) arecontrolled by a computer.

The coil size for the initial heating station 62 may be in a preferredrange relative to the part 58. Its shape may be substantially circularor in a specific shape corresponding to the part 58.

The apparatus 60 preferably has a device 78 for controlling speed anddeceleration/acceleration of the part 58 through the apparatus 60. Acomputer may control the rolls so that the part 58 can vary speed,acceleration and deceleration through entrance into the apparatus 60,each station 62, 64 and 66, and the exit of the apparatus 60. The exitspeed of the part 58 from the apparatus 60 may differ from an entrancespeed of the part 58 into the apparatus 60, although this speeddifference is not required. Controlling an exit speed of the part 58from the apparatus 60 and an entrance speed of the part 58 into theapparatus 60 may help control the quality of the part 58.

Referring to FIG. 4, in embodiments where the part 58 has an irregularcross-sectional geometry, the coil sections 70, 71 may be shaped toreflect the irregular geometry of the part 58. As used herein, the term“irregular geometry” refers to a cross-section having a non-uniformthickness, an internal void and/or at least one concavity. For example,when the part 58 is a C-channel, the coil sections 70 and 71 have ageometry that reflects the C-shape of the part 58. In this example, eachturn 72 of the coil section 70, 71 includes an outer C-shaped portion73, an inner C-shaped portion 75 and two generally U-shaped end portions77. The outer C-shaped portion 73 surrounds the outer surface 58 a ofthe part 58 on at least a portion of each of three outer sides of thepart 58. The inner C-shaped portion 75 surrounds the inner surface 58 bof the part 58 on at least a portion of each of three inner sides of thepart 58. In addition, the generally U-shaped end portions 77 surroundthe free ends 58 c of the part 58 and three sides thereof, namely anouter side portion, and end face portion and an inner side portion. Inthe configuration shown in FIG. 4, each portion 73, 75, 77 of the turn72 of the coil section 70, 71 is spaced a predetermined, and preferablyuniform, distance d1 from the respective surface 58 a, 58 b, 58 c of thepart 58. This coil configuration provides relatively fast heating of allportions of the part 58.

For some irregular geometries, the shape of the coil sections 70, 71 mayresult in areas of higher concentrations of heating. For example, whenthe part 58 is a C-channel and the coil sections 70 and 71 have ageometry that reflects the C-shape of the part 58, areas of concentratedheating may occur at the free ends 58 c of the part 58 since the freeends 58 c receive heat induction from the three sides. The concentrationof heat at the free ends 58 c makes them more prone than the otherportions 58 a, 58 b to distortion, and may negatively affect themechanical properties of the free ends 58 c and/or the part 58 as awhole.

Referring to FIG. 5, to avoid introduction of areas of concentratedheating, the coil sections 70, 70 may have an alternative geometry turn72′. The alternative geometry turn 72′ is similar to the turn 72illustrated in FIG. 4, and therefore like reference numbers will be usedto refer to like parts. In particular, the coil sections 70, 71 of theturn 72′ are shaped to reflect the C-shape of the part, and include anouter C-shaped portion 73, an inner C-shaped portion 75, and endportions 77′ that surround the three sides of the free ends 58 c of thepart 58. However, the alternative geometry turn 72′ differs from theembodiment illustrated in FIG. 4 in that the end portions 77′ have arelatively rounded, concave shape which varies a distance d2 between thethree sides of the free ends 58 c, and the end portion 77′. In someembodiments, the end portions 77′ have a shape corresponding to aportion of a circle. In all cases, the end portions 77′ of the turn 72′are spaced at least the predetermined distance d2 from the free end 58 cof the part 58. The outer and inner C-shaped portions 73, 75 remainspaced the predetermined distance d1 from their respective surfaces 58a, 58 b. The distance d2 is greater than the distance d1, and isselected so that the amount of heat received by the free end 58 c isequal to the amount of heat received in the other portions of the part58. Since the end portions 77′ are arcuate and the free ends 58 c arerectangular, the distance d2 can vary from the outer side portion to theinner side portion of the free end 58 c. The alternative geometry turn72′ provides a more uniform and controlled heating to the part 58 thanthe turn 72 illustrated in FIG. 4. As such, it may be advantageous touse the alternative geometry turn 72′ in at least the second heatingstation 66 during tempering of the part 58, if not in both heatingstations 62, 66.

The preferred speed of the part 58 through the initial heating station62 may be slower than 100 inches per minute. The speed may be variedthrough the heating station 62, the quenching station 64 and the secondheating station 66.

The relationship between the speed and coil size of the initial heatingstation 62 may be varied, and the distance and separation betweenheating stations 62 and 66 can level temperature to ensure homogeneousheating of the part 58 and its particular shape. This may avoid the needfor a separate preheating coil. Further, the first heating station 62may heat the part at a faster rate since the objective is to heat thepart as much as possible to the desired temperature and less temperaturecontrol is required. The second heating station 66 preferably provides amore controlled increase in temperature to avoid distortion of the part58. This is particularly true where the part 58 is a C-channel which canhave side edges and a central web which can heat differently from eachother and be more prone to distortion. Preferably, the speed and coilsize of each heating station 62 or 66 heat the whole part 58 at the sametime so as to heat the part 58 most uniformly or homogeneously,particularly when tempering the part 58 in the second heating station66.

FIG. 6 shows a quenching station 64 with a horizontal block 80 havingsprayers 82 and a vertical block 84 having sprayers 86. The quenching ispreferably done with liquid sprayed both longitudinally andperpendicularly. The sprayers 82 and 86 may be angled, such as towardthe direction of movement of the part 58, to preferably direct thequenching liquid in a desired direction and to avoid the liquid fromspraying into the wrong area of the apparatus 60. As an example, watermay be supplied from tubes 88 into block 80 to spray liquid via numerousclosely aligned sprayers 82.

The quenching station 64 preferably has individual quenching sections(such as 80 and 84) having different pressures and flows of liquid.Other arrangements of quenching stations are contemplated. Eachquenching section may use a liquid, such as water, for quenching thepart 58. A computer may control the individual quenching sections withdifferent pressures and flows and the direction of flow of the liquid.

The improved and variable control of the quenching station 64 uses lessliquid than the prior art. A flow of 50-150 gallons per minute forquenching is less than an estimated flow of 500-1,000 gallons per minutefor prior art quenching.

The apparatus 60 preferably includes a device 90 for controllingproximity of the part 58 to the heating coil assembly 68. A computer maycontrol the rolls so that the part 58 is passed by each heating coilassembly 68 at a desired distance, although computer control may not berequired. The part proximity may be set in a preferred range.

A process for induction heat treating and quenching a metallic part 58using an apparatus 60 includes induction heating the part 58 in acounter-wound coil assembly 68; quenching the part 58 with a liquidwhile under restraint, preferably in individual quenching sections 80and 84 using different pressures and flows; restraining the part 58 in aseries of restraining rolls during quenching; and induction heating thepart 58 again after quenching.

The process preferably includes controlling speed of the part 58 throughthe apparatus 60 including entry, each station, and exit. A computer cancontrol the speed and deceleration/acceleration of the part 58 throughthe apparatus 60 although is not required for such control. Similarly,the proximity of the part 58 to the heating coil assembly 68 can be setor controlled by a computer.

This disclosure has been described as having exemplary embodiments andis intended to cover any variations, uses, or adaptations using itsgeneral principles. It is envisioned that those skilled in the art maydevise various modifications and equivalents without departing from thespirit and scope of the disclosure as recited in the following claims.Further, this disclosure is intended to cover such variations from thepresent disclosure as come within the known or customary practice withinthe art to which it pertains.

What is claimed is:
 1. An apparatus that performs induction heattreatment of a part, the apparatus comprising: rolls to convey, guideand restrain the part as it passes through the apparatus; a firstheating station including a first heating coil assembly, the firstheating coil assembly including a coil section configured to surroundthe part, the coil section having a spacing relative to an outer surfaceof the part that varies along the outer surface of the part in such away that induction heating of the part is uniform regardless of thecross sectional geometry of the part; a device that controls varyingspeed of the part through the apparatus; and a quenching station withindividual quenching sections having different pressures and flows of aliquid.
 2. The apparatus of claim 1, wherein the part has a C-shapedcross section, and the coil section includes an outer C-shaped portionthat surrounds a portion of an outer surface of the part, an innerC-shaped portion that surrounds a portion of an inner surface of thepart, and end portions that surround free ends of the part.
 3. Theapparatus of claim 2, wherein at least one of the outer C-shaped portionand the inner C-shaped portion is spaced a distance d1 from a surface ofthe part, and the end portions are spaced a distance d2 from the part,where the distance d2 is greater than the distance d1.
 4. The apparatusof claim 2, wherein the end portions of the coil section are concave. 5.The apparatus of claim 2, wherein the end portions of the coil sectionare rounded.
 6. The apparatus of claim 2, wherein the end portions ofthe coil section have a shape corresponding to a portion of a circle. 7.The apparatus of claim 1 further comprising a device that controlsproximity of the part to the heating coil assembly.
 8. The apparatus ofclaim 1, wherein the first heating coil assembly includes two coilsections, and the two coil sections are wound in opposite directions. 9.The apparatus of claim 8 further comprising a second heating stationdownstream of said quenching station, wherein the second heating stationincludes a second heating coil assembly having two coil sections woundin opposite directions.
 10. The apparatus of claim 1 wherein the firstheating coil assembly includes a first coil section and a second coilsection that is wound in a direction opposite to that of the first coilsection, and induction on the first coil section is performed from onedistal end of the coil to the other extreme, and induction on the secondcoil section is performed in an opposite direction wherein the firstheating coil assembly provides substantial magnetic neutralization. 11.A process for induction heat treating including quenching a metallicpart of a vehicle structural frame in an apparatus, the processcomprising: controlling speed of the part through the apparatus;induction heating the part in a heating station including a heating coilassembly, the heating coil assembly including a coil section configuredto surround the part, the coil section having a spacing relative to anouter surface of the part that varies along the outer surface of thepart in such a way that induction heating of the part is uniformregardless of the cross sectional geometry of the part; quenching thepart with a liquid while under restraint, including the step ofrestraining the part in a series of restraining rolls during quenching;and induction heating the part again after quenching.